In recent years, as portable electronic devices (e.g., mobile phones and digital cameras) become ubiquitous, much effort has been put into reducing dimensions of portable electronic devices. Moreover, as dimensions of charged coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) based optical sensors are reduced, dimensions of imaging lenses for use with the optical sensors must be correspondingly reduced without significantly compromising optical performance. Imaging quality and size are two of the most important characteristics for an imaging lens.
Each of U.S. Pat. Nos. 7,692,877 and 8,325,269, Taiwan Patent No. 1320107 and Japan Patent Application Publication No. 2006-293324 discloses a conventional imaging lens that includes four lens elements. However, a system length of such kind of conventional imaging lenses is not reducible to be within a range that meets the thin product design requirements of mobile phones.
Therefore, greater technical difficulties are encountered for a miniaturized imaging lens than for traditional imaging lenses. Producing an imaging lens that meets the requirements of consumer electronic products while having satisfactory optical performance is always a goal in the industry.